Fuse



T. BIRKENMAIER FUSE Filed July 14, 1958 3 Sheets-Sheet 1 FIG .4.

Oct. 17, 1939. T. BIRKENMAIER FUSE Filed July 14, 1938 3 Sheets-$heet 3 FIG],

Patented Oct. 17, 1939 FUSE Theodore Birkenmaier, St. Louis, Mo., assignor to W. N. Matthews Corporation, St. Louis, Mo., a

corporation of Missouri Application July 14, 1938, Serial No. 219,131

12 Claims.

This invention relates to fuses, and with regard to certain more specific features, to expulsion fuses.

The invention is an improvement upon the construction shown in my United States Patents 2,077,207 and 2,135,789, dated April 13, 1937, and November 8, 1938, respectively.

Among the several objects of the invention may be noted the objects set forth in the above patent but wherein the advantageous knife-type of contact referred to in the above application is used; the provision of apparatus of the class described which eliminates the necessity for the added contact disclosed in the application; and

the provision of apparatus of this class in which theoperation of closing a door results in a relatively high unit pressure for attaining proper 4 electrical contact, but in which tension on the fuse link will not be excessive. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated one of various possible embodiments of the invention;

Fig. l is a vertical section showing a fuse box in its circuit-closing position;

Fig. 2 is a view similar to'Fig. 1, but showing a first movement as a disconnection occurs;

Fig. 3 is a view similar to Fig. 2 showing a final position of parts after disconnection;

Fig. 4 is an inside view of the door of the box with fuse holder parts thereon in the position such as shown in Fig. 1;

Fig. 5 is an inside view of the fuse box with the door and fuse holder removed;

Fig. 6 is a horizontal section taken on line 6-6 of Fig. 1;

Fig. 7 is a horizontal section taken on line 'l-1 of Fig. 2; and, 1

Fig. 8 is a vertical section taken on line 8-4 of Fig. 7.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

In my Patent 2,077,207, I show an expulsio fuse construction in which the fuse link, after melting, and expulsion from a fuse tube, hangs from the fuse unit in an unelectrified condition,

with a wide separation of the separated link 7) and downwardly (see Fig. 5).

ends. While the apparatus of that patent. is effective, it is desirable, (under certain circumstances, to employ a so-called knife contact means. For example, where a low temperature rise is desired, such knife contacts are desirable. 5 The use of such knife contacts, in the case of the patent, would present too much friction to downward movement of the lower movable terminalengaging element of the patent. F

In the application above referred to, a knife 10 contact arrangement is shown, but in that construction there has been eliminated the requirement of movement of the lower terminal-engaging element. Instead, an added contactis em-' ployed which forms the required movement. 15

By means of the present invention, the advantages of the knife contactsare obtained without the employment of the added contact.

Referring now more particularly to Fig. 1, there is shown at numeral I a box madeof insulating 20 material such as porcelain adapted to be supported by means of bolts 3 and having anchored thereinconducting line terminals 5. The line terminals include wire clamps 1 for respective wires 8. Associated with the upper line terminals 25 5 are riveted U-shaped spring conducting members forming a knife contact 9. This contact is of the variety in which the opposite faces of the spring members are substantially parallel.

To the lower line terminal 5 is riveted a different type of spring conducting member Hi. This conducting member I0 is characterized by the fact that the inner spring arms are fiared outwardly toward the front of the box I (See Fi These inner 35 arms are of about the same springiness as the known type of spring arms forming the knife contacts 9.

The box I is open at the bottom as indicated at II; It also has a front opening i3 covered by 40 a door l5 hinged on a pin IT. The hook-shaped portion IS on the door which eifectshinging is open as shown at 2| so that the door may be removed from the box after it has been pulled to an open position. A ring 23 is provided for manipu- 45 lating the door. The door I5 is' made of insulating material, such as Bakelite, for example.

The door 15 has attached thereto, by means of screws 25, an upper terminal-engaging element 21. This terminal-engaging element 21 is made 50 of conducting material and is hollow. It has flat sides 3| for engagement with the flat sides of the U-shaped spring conducting contact 9 of upper line terminal 5.

The spring pressure between the spring arms 55 of contact 9 and the terminal-engaging element 21 is substantial, so that a good contact is obtained under operating conditions without undue temperature rise in the switch. This also induces friction which maintains the door l5 in closed condition, but which permits of pulling the door open when desired.

The hollow portion of the upper terminalengaging element 21 is open at the top and bottom, and at the top it is threaded to receivea threaded enclosing cap 35. The cap also functions as a clamp for the upper headed end 31 of a fuse link 39. The fuse link 39 has a fusible portion 4| adapted to melt upon overload and to open the circuit. Its lower end is composed of flexible conducting wire, as indicated at 43.

The fuse link 39, 43 passes through an insulating tube 45 which is rigidly supported at its upper end by the upper terminal-engaging element 21. This tube 45 is steadied by a support 28, said support extending from the door l5. The lower end of the tube 45 is open, as indicated at 41, and has an open notch 49 at one side. A septum 52 associated with the box forms a saddle around the tube 45, and with the adjacent support 28 divides the box roughly into an upper and lower compartment, which tends to prevent current leakage between the line terminals 5.

Slidably arranged on the extending lower end of insulating tube 45 is a second insulating tube or sleeve 5|.

The lower end of the sleeve 5| is provided with a fixed collar 51 which may or may not be made of conducting material, although in the present embodiment it is so shown. This collar is formed on one side with a smooth, rounded, anti-friction saddle 59. The notch 49 in fixed tube 45 cooperates with the inner edge of the saddle 59 to properly direct the fuse link into tube 45. The end of the notch 49 also forms a stop for the saddle 59 for purposes which will appear.

The top of the collar 51 forms a seat for a spring 6|. Above the spring 6| and slidably arranged upon the outside of the sleeve 5| is a lower terminal-engaging element 63. This element or contact carries a screw 65, the end of which extends into a slot 53 arranged in the tube 5|. The slot 53 is of limited length and limits relative longitudinal movement between the contact elements 63 and the tube 5|.

The element 63 is of special inverse form to mate with the lower line terminal III, that is, the contact 63 tapers inwardly with respect to the door l5 and upwardly. Conversely stated, it is shaped so as to flare outwardly toward the door I5 and to flare downwardly. It is evident that the pin in the groove 53 prevents relative rotary movement between the lower contact or terminal-engaging element 63 and tube 5|. To prevent relative rotation between the tubes 5| and 45, but to permit relative longitudinal movement, the back of the lower terminal-engaging element 63 has formed therewith a pad I! which by cooperation with a pad l4 on the door l5 permits longitudinal movement but prevents rotation, as stated.

The upper limit of motion of the assembly of tube 5|, collar 51, spring 6| and member 63 with respect to the tube 45, is determined by cooperation between the inner portion of the saddle 59 and the end of the notch 49. The lower limit of motion is determined by contact between the pad I! and a stop pin 6 on the door |5.

Associated with the terminal-engaging element 63 is a clamp-nut combination 68 on a threaded stud 66, by means of which the lower end of the fuse link 43 may be bound to the terminal-engaging element 63.

Operation of the device is as follows, assuming that the door l5 has been removed, and that a new fuse is required:

The cap 35 is removed and the old upper fuse element removed. Such lower fuse element as may be held by the clamp nut 68 is also removed.

The new fuse is fed (flexible part 43 first) through the upper terminal-engaging element 21 and its head 31 is clamped in position by the enclosing cap 35. The lower end of the fuse then extends from the lower end opening 41 of the tube 45 and from the lower open end 61 of the ring 51. It is threaded around the saddle 59 and then turned upwardly and its ends fastened by means of the clamp 68. By drawing as much as possible of the fuse 43 from the tube 45, under these conditions, the assembly of collar 51, spring 6|, tube 5|, and terminal-engaging element 63 is raised as high as possible with respect to the stationary tube 45. However, the operator does not manually stretch the fuse nor does he tension spring 6|. He simply takes all of the slack out of the fuse link without tensioning spring 6|.

Next, the door l5 has its hook |9 applied over the pin l1 and the door is then rotated up into closed position, as shown in Fig. 1. This causes the upper terminal-engaging element 21 to be frictionally engaged by spring arms 9 of the line terminal 5.

The lower terminal-engaging element 63 is at this time at such an elevation on door l5 that it is springingly engaged by the spring arms In of the lower line terminal. The reaction between the outwardly and downwardly flowing line arms I0 and the upwardly and inwardly tapered terminal-engaging element 63 causes the latter to be pressed downwardly against the spring 6| to compress the latter. By this means, the saddle 59 is forced down by spring 6| and is caused to tension the link 43. The tension in the link 43 is desirable for knownreasons. At the same time, the reaction between the terminal-engaging element 63 and the line terminal l0 causes a satisfactory surface contact (preferably not point or line contact) which has the effect of preventing the building up of switch temperatures by reducing resistance at this point. The surfaces between the terminal-engaging element 63 and line terminal H) are so arranged that the component of force exerted downwardly is of a proper degree properly to tension the fuse link.

Upon overload, the reduced fuse portion 4| melts. This releases the saddle 59. The spring 6| having theretofore been under compression forces the saddle down, since the terminal-engaging element 63 cannot further be forced upward in line terminal l6. The saddle 59 bein associated 'with the collar 51 draws down the tube 5| until the upper end of the slot 53 strikes the end of screw (Fig. 2). This supplies an impact blow to the lower terminal-engaging element 63 to drive it away from engagement with the line terminal ll (Fig. 3). It is to be understood, however, that even without this blow the spring squeezing action of the lower outwardly and downwardly flared line terminal ll would normally squeeze the terminal-engaging element 63 out and down so that the latter would be out of contact. It will be understood that at this time there is also an expulsive action through the fact that all contacts are surface contacts, one

element of each contact being composed of springy material so as to maintain the proper resilient contact pressure.

Another advantage is that the separable terminal-engaging element 63 and line terminal Ill cannot stick, even under roughened conditions,

because of the sharp blow delivered when the spring 6| expands.

Another feature is that the squeezing action of the lower line terminal III has a tendency both to tension the fuse link and to force the terminalengaging element 63 out of contact upon blowing of the fuse link.

Another advantage is that the contact pressure between the terminal-engaging element 63 and the lower line terminal [0 may be made high without imposing a proportionately high tension on the fuse link. This is accomplished by properly proportioning the outward and downward flares to give the desired forced ratios.

It will be understood from the showing in the drawings that the friction between the upper terminal 9 and the upper engaging element 3| is enough to hold shut the door l5 against the small outward reaction between the lower terminal l0 and the lower engaging element 63.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus of the class described, a base, spaced line terminals thereon; a hinged member on the base, a fixed terminal-engaging element on said hinged member and cooperable with one of said line terminals, a movable terminal-engaging element on said hinged member, a fuse link connecting said terminal-engaging elements, tubular meansthrough which said link passes and with respect to which the movable terminal-engaging element moves, said fuse link having a,

turn around the end of said tube, resilient means tending to separate the movable terminal-engaging element and said tube so as to locate the movable terminal-engaging element in elevated position, and cooperating surfaces between said movable terminal-engaging element and its respective line terminal whereby when said hinged member is moved to cause cooperation between the terminal-engaging elements and the line terminals, said spring is automatically tensioned and tension is placed in the fuse link.

2. In apparatus of the class described, a base, spaced line terminals thereon, a hinged member on the base, a fixed terminal-engaging element on said hinged member and cooperable with one of said line terminals, a fixed tube extending from the last-named line terminal-engaging element, a movable terminal-engaging element on said hinged member, a fuse link connecting said terminal-engaging elements, movable tubular means slidable on the fixed tube through which passes said link and with respect to which the movable terminal-engaging element moves, said fuse link having a turn around the-end of said tube and passing through the fixed tube, spring means between the movable terminal-engagingelement and said movable tube adapted to locate the movable terminal-engaging element in elevated position, and cooperating surfaces between said movable terminal-engaging element and its respective line terminal whereby when said hinged member is moved to cause cooperation between the terminal-engaging elements and the line terminal, said spring is automatically tensioned and tension is placed in the fuse link, said spring means upon blowing of the link forcing the movable tube relatively to the movable terminal-engaging element to aid in forcing the latter from its line, contact.

3. In apparatus of the class described, a base, spaced line terminals thereon, a hinged member on the base, a fixed terminal-engaging element on said hinged member and cooperable with one of said line terminals, a movable terminal-en- I gaging element on said hinged member, a fuse link connecting said terminal-engaging elements, movable tubular means through which passes said link and with respect to which the movable terminal-engaging element moves, said fuse link having a turn around the end of said tube, resilient means between the movable terminal-engaging element and said tube adapted to locate the movable terminal-engaging element in elevated position, cooperating surfaces between said movable terminal-engaging element and its respective line terminal whereby when said hinged member is moved to cause cooperation between the terminal-engaging elements and the line terminals, said spring is tensioned and tension is placed in the fuse link, and stop means-between the tube and the movable terminal-engaging element adapted to provide'a blow, upon the expansion of said spring, to remove the movable terminal-engaging element from its line terminal, the terminal-engaging element and tubular means being thereafter movable by gravity to draw down the link.

4. In apparatus of the class described, a base, spaced line terminals thereon, a hinged member on the base, a fixed terminal-engaging element on said hinged member and cooperable with one of said line terminals, a movable terminal-engaging element on said hinged memberfa fuse link connecting said terminal-engaging elements, movable tubular means through -.which passes said link and with respect to which the movable terminal-engaging element moves, said fuse link having a turn around the end of said tube, resilient means between the movable terminal-engaging element and said tube adapted to locate the movable terminal-engaging element in elevated position, cooperating surfaces between said movable terminal-engaging element and its respective line terminal whereby when said hinged member is moved to cause cooperation beexpansion of said spring, to remove the movable terminal-eiigaging element from its line terminal, the terminal-engaging element and tubular means being thereafter movable by gravity to draw down the link, and a fixed tube for slidably supporting the movable tube.

5. In apparatus of the class described, a base, spaced line terminals thereon, a hinged member on the base, a fixed terminal-engaging element on said hinged member and cooperable with one of said line terminals, a movable terminal-engaging element on said hinged member, a fuse link connecting said terminal-engaging elements, movable tubular means through which passes said link and with respect to which the movable terminal-engaging element moves, said fuse link having a turn around the end of said tube, resilient means between the movable terminal-engaging element and said tube adapted to locate the movable terminal-engaging element in elevated position, cooperating surfaces between said movable terminal-engaging element and its respective line terminal whereby when said hinged member is moved to cause cooperation between the terminal-engaging elements and the line terminals, said spring is tensioned and ten sion is placed in the fuse link, and stop means between the tube and the movable terminal-engaging element adapted to provide a blow upon the expansion of said spring to remove the movable terminal-engaging element from its line terminal, the terminal-engaging element and tubular means being thereafter movable by gravity to draw down the link, a fixed tube for slidably supporting the movable tube, and a stop on this) door for limiting the descent of said movable 6. In apparatus of the class described, a support, line terminals on the support, both of said terminals being of the spring-clip type, the lower one of which has outwardly and downwardly flaring surfaces, a fuse holder comprising a relatively fixed terminal-engaging element, and a second terminal-engaging element longitudinally movable with respect thereto, a fuse link having a turn joining said terminal-engaging elements, spring means reacting between the lower terminal-engaging element and the fuse link to tension the latter, said lower terminal-engaging element being positioned when the link is in place springingly to engage said flared line terminal.

'7. In apparatus of the class described, a. base,

' line terminals thereon, one of which comprises spring arms outwardly and downwardly flared and adapted for surface contact, a fuse holder movable with respect to said base and comprising a fixed terminal-engaging element, a stationary tube extending therefrom having an open lower end, a movable tube on the stationary tube, a terminal-engaging element slidable on said movable tube, spring means reacting between said movable terminal-engaging element and said slidable tube, a fuse link joining said fixed terminal-engaging element and said mov- 'able terminal-engaging element, said movable terminal-engaging element being formed to cooperate with the flare of. said flared line terminal whereby a force is obtained tending to move the movable terminal-engaging element on said movable tube.

an outward and downward flare, a fuse holder,

a fixed terminal-engaging element on said fuse holder adapted to cooperate with the upper line terminal, a movable terminal-engaging element having flared surfaces adapted to cooperate with said lower line terminal, a fuse link joining said terminal-engaging elements, said fuse link having a turn, and resilient means between said movable terminal-engaging element and the fuse link at the turn.

9. In apparatus of the class described, a base, upper and lower line terminals thereon, the lower line terminal having spring arms adapted to effect surface contact and being provided with an outward and downward flare, a fuse holder, a fixed terminal-engaging element on said fuse holder adapted to cooperate with the upper line terminal, a movable terminal-engaging element having flared surfaces adapted to cooperate with said lower line terminal, and a fuse link joining said terminal-engaging elements.

10. In apparatus of the class described, a base, upper and lower line terminals thereon, the lower line terminal having spring arms adapted to effect surface contact and being provided with an outward and downward flare, a fuse holder, a fixed terminal-engaging element on said fuse holder adapted to cooperate with the upper line terminal, a movable terminal-engaging element having flared surfaces adapted to cooperate with said lower line terminal, a fuse link joining said terminal-engaging elements, said fuse link having a turn, and resilient means between said movable terminal-engaging element and the fuse link at the turn.

11. In apparatus of the class described, spaced line terminals, a support movable with respect to said line terminals, a terminal-engaging element on said support, said terminal-engaging element being fixedly cooperable with one of said line terminals, a movable terminal-engaging element on said movable support, a fuse link connecting said terminal-engaging elements, means movable with respect to the support around one end of which said link passes and with respect to which saidmovable terminal-engaging element is also movable, and resilient means tending to push apart the movable terminal-engaging element and said movable means so as normally to locate the movable terminal-engaging element at a position for engagment with a line terminal.

12. In apparatus of the class described, spaced line terminals, a support movable with respect to said line terminals, a terminal-engaging element on said support, said terminal-engaging element being fixedly cooperable with one of said line terminals, a movable terminal-engaging element on said movable support, a fuse link connecting said terminal-engaging elements, means movable with respect to the support around one end of which said link passes and with respect to which said movable terminal-engaging element is also movable, resilient means tending to push apart the movable terminal-engaging element and said movable means so as normally to locate the movable terminal-engaging element at a position for engagement with a line terminal, and stop means between the movable means and the movable terminal-engaging element adapted upon the expansion of said resilient means to effect a blow on the movable line terminal-engaging element so as positively to remove it from its line terminal.

THEODORE BIRKENMAIER. 

